JP2014144611A - Inkjet recorder and ink charging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely control temperature of an ink to a target one without being greatly affected by capability of a heating part for heating the ink, and to fill the inside of a flow path of an unfilled head module with the ink without leaving air bubbles.SOLUTION: An inkjet head (72) is composed of a plurality of head modules (72-i). Each head module (72-i) is connected in parallel between a supply-side manifold (214) and a recovery-side manifold (218) through a supply-side shut-off valve (222) and a recovery-side shut-off valve (226). A bypass flow path (232) joining the supply-side manifold (214) and the recovery-side manifold (218), and an ink temperature regulation part (258) regulating the ink temperature are provided. Before early filling of the head module with the ink, the ink is circulated by utilizing the bypass flow path (232), and also the ink is heated by the ink temperature regulation part. After the ink is circulation-heated to a target temperature, the ink is filled in the head module of a filling object.

Description

  The present invention relates to an ink jet recording apparatus and an ink filling method, and more particularly, to an ink supply technique when initially filling ink into a head module not filled with ink.

  In an ink jet recording apparatus, in order to perform normal ejection from the nozzles of the print head, it is necessary that the print head is sufficiently filled with ink. The “sufficient filling” described here means that a large number of nozzles inside the head module are filled without any unfilled nozzles.

  When the ink is filled into the flow path in the head that has not been filled with ink (initial filling), such as when the head is replaced with a new head due to a head failure, etc., the wettability determined by the physical properties of the ink and the inner wall of the flow path Is particularly important. When the wettability is good, ink is filled without bubbles in the unfilled flow path, but when the wettability is poor, the remaining bubbles in the flow path become significant and the flow path cannot be sufficiently filled with ink. .

  The wettability is determined by the physical property value of the inner wall of the flow channel, the flow channel shape, and the physical property value of the ink. Further referring to the physical property values of the ink, the lower the surface energy (surface tension) of the ink, the easier it is to bond between different substances, so that the wettability of the ink is improved.

  Regarding the ink filling method for the print head, the techniques described in Patent Documents 1 to 3 are known. In Patent Documents 1 and 2, a means for heating the liquid in the flow path is provided in front of the head in the path for supplying ink to the head, and a configuration in which the heated liquid is filled in the head is employed. On the other hand, in Patent Document 3, there is a method for improving the initial ink filling property by increasing the temperature on the flow path side of the head unit without controlling the ink temperature, because the print head unit has a heating mechanism. Proposed.

Japanese Patent Laid-Open No. 11-207993 JP 2009-12347 A Japanese Patent Laid-Open No. 1-156074

  In Patent Documents 1 and 2, heating means (heating unit) is provided in front of the head, but there is no particular mention regarding the configuration of the ink flow path suitable for temperature control. According to Patent Document 1, a plurality of ink pressure chambers constituting a print head are connected in series between an ink supply pipe and an ink return pipe (see FIG. 1 of Patent Document 1), and in front of the print head. Ink temperature controllability by the heating means is poor. In Patent Document 1, a temperature detection sensor is arranged on the downstream side of the heating unit, and a configuration in which the heater ON / OFF of the heating unit is controlled based on the detection result of this sensor is employed. In some cases, the print head may be filled with ink without being sufficiently heated. In order to prevent air bubbles from being mixed during ink filling with the configuration of Cited Document 1, it is necessary to sufficiently heat the ink to the target temperature by heating means disposed in front of the print head and then allow the ink to flow into the print head. The heating means is required to have sufficient heating capacity.

  Also in the configuration of Patent Document 2, there is only one ink flow path from the ink cartridge to the head, and there is a concern that the ink flows into the head without being sufficiently heated by the heating unit. In addition, Patent Document 2 does not mention the place where the ink temperature is measured, and it is not clear which temperature is measured and used as a reference for temperature control. In the configuration of Patent Document 2, as in Patent Document 1, the ink temperature greatly depends on the heating performance of the heating unit.

  Patent Document 3 proposes a configuration in which the flow path side of the head is heated instead of ink heating control. However, the configuration described in Patent Document 3 has poor heating efficiency, and a large heater is required to heat the inside of the head to a target temperature. Moreover, uniform heating is difficult.

  The present invention has been made in view of such circumstances, and can solve the above-described problems and reliably control the temperature of the ink to the target temperature without being greatly affected by the ability of the means for heating the ink. An object of the present invention is to provide an ink jet recording apparatus and an ink filling method capable of filling ink without leaving bubbles in the flow path of the head module not filled with ink.

  In order to solve the above problems, the following aspects of the invention are provided.

  (First Aspect): An ink jet recording apparatus according to a first aspect includes an ink jet head composed of a plurality of head modules and a supply side in which the plurality of head modules are connected in parallel and supplies ink to each head module. A manifold, a plurality of head modules are connected in parallel, a recovery-side manifold that recovers ink from each head module, and a head that is provided corresponding to each head module and connects each head module to the supply-side manifold. A supply-side on-off valve capable of opening and closing one flow path, a recovery-side on-off valve provided corresponding to each of the head modules, and capable of opening and closing a second flow path connecting each head module and the recovery-side manifold; A plurality of head modules are connected in parallel between the side manifold and the collection side manifold. A bypass channel connecting the side manifold and the recovery side manifold, a bypass on-off valve capable of opening and closing the bypass channel, a supply side pump for varying the pressure of the supply side channel including the supply side manifold, and a recovery side manifold A recovery-side pump that varies the pressure of the recovery-side flow path including the ink temperature adjustment unit that adjusts the temperature of ink supplied to the head module, a supply-side on-off valve, a recovery-side on-off valve, a bypass on-off valve, and a supply-side pump , A recovery side pump, and a control unit that controls the operation of the ink temperature adjusting unit, and the control unit circulates the ink using the bypass flow path and supplies the ink before the head module is initially filled with ink. After the ink is heated by the temperature control unit and the ink is circulated and heated to the target temperature, the heated ink is filled in the head module to be filled. An ink jet recording apparatus which performs control to.

  According to the first aspect, before the initial filling, the ink is heated by the ink temperature adjusting unit while opening the bypass opening / closing valve, allowing the ink to flow through the bypass flow path, and circulating the ink using the bypass flow path. By such circulation heating using the bypass flow path, the ink can be sufficiently heated to the target temperature without being greatly affected by the ability of the ink temperature adjusting unit. Then, the ink can be filled into the unfilled head module while being sufficiently heated to the target temperature. The surface tension of the ink is strongly related to the temperature, and the surface tension tends to decrease as the ink temperature increases. Therefore, it is possible to fill the head module with ink at a high ink temperature (a good wettability state), and to prevent remaining bubbles.

  (Second aspect): In the ink jet recording apparatus according to the first aspect, at least one of the supply-side manifold and the recovery-side manifold is provided with a temperature sensor, and the control unit determines the ink temperature based on information obtained from the temperature sensor. It can be set as the structure which controls an adjustment part.

  According to the second aspect, since the ink temperature can be detected at a position close to the head module, the ink temperature can be adjusted with high accuracy. In addition, the configuration in which the temperature sensor is installed in the supply side manifold and / or the recovery side manifold, which is a flow path common to the plurality of head modules, is a temperature sensor compared to the mode in which the temperature sensor is installed in each head module. Therefore, the cost can be reduced.

  (Third Aspect): In the ink jet recording apparatus according to the second aspect, the control unit sets a temperature that is a target value for temperature control, and feedback-controls the ink temperature adjustment unit using information obtained from the temperature sensor. It can be configured.

  According to the third aspect, the temperature of the ink circulated using the bypass flow path is monitored by the temperature sensor, and the operation of the ink temperature adjusting unit is controlled so as to reach the target ink temperature. Thereby, the ink temperature can be adjusted with higher accuracy.

  (Fourth aspect): In the ink jet recording apparatus according to any one of the first to third aspects, the ink temperature adjusting unit has a temperature adjusting function for both heating and cooling of the ink. it can.

  In order to change the temperature control target value (temperature set value) and adjust the temperature to the target ink temperature in a short time, there is a configuration that employs an ink temperature control unit that has both a heating function and a cooling function. preferable.

  (Fifth aspect): In the ink jet recording apparatus according to any one of the first to fourth aspects, the ink filling temperature at the time of initial filling is the printing at the time of image recording using an ink jet head. It can be set as the temperature set higher than the service temperature.

  The temperature of the ink when ejecting ink droplets from the nozzle (ink ejection port) of the ink jet head and performing image recording (printing) is the meniscus recovery time (refill time) after ejecting the ink droplets from the nozzle. affect. When the ink temperature is too high and the surface tension of the ink is excessively small, the meniscus recovery time becomes long, and printing at the intended ejection frequency becomes difficult. Therefore, it is suitable for printing so that the ink temperature (printing temperature) at the time of normal ink supply for supplying ink to the inkjet head for printing is the surface tension that enables printing at a predetermined discharge frequency. Temperature range.

  On the other hand, the ink temperature (ink filling temperature) at the initial filling is set to a temperature higher than the printing temperature so as to lower the surface tension from the viewpoint of improving wettability.

  By setting the ink temperature according to the purpose for printing and for ink filling, the optimum operation corresponding to each is guaranteed.

  (Sixth aspect): In the ink jet recording apparatus according to the fifth aspect, the ink filling temperature may be 70 ° C. or less.

  The upper limit of the ink filling temperature is preferably determined within a range in which the ink is not deteriorated. Although the maximum temperature may vary depending on the composition of the ink, most of the ink used for ink jet printing is suitably set to 70 ° C. or lower.

  (Seventh aspect): In the ink jet recording apparatus according to the fifth aspect or the sixth aspect, the entire ink jet head after ink filling is completed or a part of a plurality of head modules is replaced. In this case, the control unit can change the ink temperature setting from the printing temperature to the ink filling temperature.

  When printing is performed after ink filling is completed, the ink temperature is adjusted to the printing temperature. After that, when the entire inkjet head or a part of the head module is replaced due to a head failure, etc., the ink temperature is changed to an ink filling temperature higher than the printing temperature. The initial filling property of the ink to the mounted head module can be improved.

  (Eighth aspect): In the ink jet recording apparatus according to the seventh aspect, after the initial filling of the ink to the head module newly mounted by replacement is completed, the control unit sets the ink temperature to the printing temperature. It can be set as the structure which performs control to change.

  After completion of ink filling, it is preferable to start printing after returning the ink temperature to the printing temperature.

  (Ninth aspect): In the ink jet recording apparatus according to any one of the first aspect to the eighth aspect, the ink jet head is a line head bar in which the head module can be replaced in units of head modules. can do.

  It is preferable that each head module can be replaced with a new head module when some of the head modules are deteriorated (failed). In this case, circulation heating using the bypass flow path is performed before the initial replacement of ink in the replaced new head module (head module not filled with ink), and after the target temperature is sufficiently heated, the filling is performed. Is done.

  (Tenth aspect): In the ink jet recording apparatus according to any one of the first to ninth aspects, the control unit includes at least a supply-side on-off valve and a collection-side on-off valve connected to a head module to be initially filled. In this configuration, after the ink is heated to the target temperature, the supply side on-off valve and the recovery side on-off valve connected to the head module to be initially filled are opened. be able to.

  As a specific control mode by the control unit, before the head module not filled with ink is filled with ink, the supply side opening / closing valve and the collection side opening / closing valve connected to the unfilled head module are closed. After the ink is circulated and heated to the target temperature using the bypass flow path, the supply side open / close valve and the collection side open / close valve are opened, and the flow path is opened to introduce the ink into the head module. Control can be employed.

  (Eleventh aspect): The ink filling method according to the eleventh aspect is an ink jet head composed of a plurality of head modules and a supply in which a plurality of head modules are connected in parallel to supply ink to each head module. A side manifold, a plurality of head modules are connected in parallel, a recovery side manifold for recovering ink from each head module, and a corresponding one for each head module are connected to each head module and the supply side manifold. A supply-side on-off valve capable of opening and closing the first flow path, a collection-side on-off valve provided corresponding to each of the head modules, and capable of opening and closing the second flow path connecting each head module and the collection-side manifold; A plurality of head modules are connected in parallel between the supply side manifold and the recovery side manifold for supply Includes a bypass flow path connecting the manifold and the recovery side manifold, a bypass on-off valve that can open and close the bypass flow path, a supply side pump that varies the pressure of the supply side flow path including the supply side manifold, and a recovery side manifold An initial ink filling method for a head module in an ink jet recording apparatus, comprising: a collection-side pump that varies the pressure of a collection-side flow path section; and an ink temperature adjustment section that adjusts the temperature of ink supplied to the head module. Before the head module is initially filled with ink, a circulation heating process for circulating the ink to the target temperature by circulating the ink using the bypass flow path and heating the ink by the ink temperature adjusting unit, and the circulation heating Ink heated by the process is caused to flow into the head module to be filled to fill the ink. A step Hama, an ink filling method comprising.

  In the ink filling method according to the eleventh aspect, the configurations according to the second aspect to the tenth aspect can be appropriately combined.

  According to the present invention, the temperature of the ink can be accurately adjusted to the target temperature without being greatly affected by the ability of the ink temperature adjusting unit, and the head module not filled with ink is in a state of good wettability. Ink can be filled. Thereby, ink can be filled without leaving bubbles in the flow path of the head module.

Configuration diagram showing overall configuration of inkjet recording apparatus A perspective view showing a configuration example of an inkjet head Partial enlarged view of inkjet head viewed from nozzle side Plane perspective view of the head module An enlarged view of a part of FIG. 4A Longitudinal sectional view showing the internal structure of the head module Schematic configuration diagram of ink supply unit The block diagram which shows schematic structure of the control system of the ink supply apparatus shown to this example The flowchart which shows the 1st example of the operation | movement procedure of the ink filling process accompanying replacement | exchange of a head module. The flowchart which shows the 2nd example of the operation | movement procedure of the ink filling process accompanying replacement | exchange of a head module. Flowchart illustrating the operation procedure of temperature adjustment processing after ink filling Block diagram showing schematic configuration of control system of inkjet recording apparatus

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Overall configuration of inkjet recording apparatus]
First, the overall configuration of an ink jet recording apparatus to which the present invention is applied will be described. FIG. 1 is a configuration diagram showing the overall configuration of an ink jet recording apparatus according to an embodiment of the present invention. As shown in the figure, the ink jet recording apparatus 10 according to the present embodiment mainly includes a paper feeding unit 12, a processing liquid application unit 14, a drawing unit 16, a drying unit 18, a fixing unit 20, and a discharge unit 22. The

<Paper Feeder>
The paper supply unit 12 is a mechanism that supplies a sheet 24 as a recording medium to the processing liquid application unit 14. Sheets 24 that are sheets are stacked on the sheet feeding unit 12. The paper feed unit 12 is provided with a paper feed tray 50, and the paper 24 is fed from the paper feed tray 50 to the processing liquid application unit 14 one by one.

  As the paper 24 as a recording medium, general-purpose printing paper (paper mainly composed of cellulose) is used. Note that the type of the recording medium is not limited to this. In this example, a sheet (cut paper) is used, but a configuration in which a roll paper is cut to a required size and fed is also possible.

<Processing liquid application part>
The processing liquid application unit 14 is a mechanism that applies the processing liquid to the recording surface of the paper 24. The treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment in this example) applied in the ink provided by the drawing unit 16, and the ink comes into contact with the colorant when the treatment liquid comes into contact with the ink. And the solvent are promoted.

  As shown in FIG. 1, the treatment liquid application unit 14 includes a paper supply drum 52, a treatment liquid drum 54, and a treatment liquid application device 56. The treatment liquid drum 54 is a drum that holds the sheet 24 and rotates and conveys the sheet 24. The treatment liquid drum 54 is provided with a claw-shaped holding means (gripper) 55 on its outer peripheral surface, and the paper 24 is sandwiched between the claw of the holding means 55 and the peripheral surface of the treatment liquid drum 54 so that the front end of the paper 24 is moved. It can be held. The treatment liquid drum 54 may be provided with suction holes on the outer peripheral surface thereof and connected to suction means for suction from the suction holes. As a result, the sheet 24 can be held in close contact with the peripheral surface of the treatment liquid drum 54.

  A processing liquid coating device 56 is provided outside the processing liquid drum 54 so as to face the peripheral surface thereof. The treatment liquid coating device 56 is disposed on the treatment liquid container in which the treatment liquid is stored, the anix roller partially immersed in the treatment liquid in the treatment liquid container, and the sheet 24 on the anix roller and the treatment liquid drum 54. It is composed of a rubber roller that is in pressure contact and transfers the measured processing liquid to the paper 24. According to the processing liquid application device 56, the processing liquid can be applied to the paper 24 while being measured.

  The sheet 24 to which the processing liquid is applied by the processing liquid applying unit 14 is transferred from the processing liquid drum 54 to the drawing drum 70 of the drawing unit 16 via the intermediate transport unit 26.

<Drawing part>
The drawing unit 16 includes a drawing drum 70, a paper holding roller 74, and ink jet heads 72M, 72K, 72C, 72Y. The drawing drum 70 includes a claw-shaped holding means (gripper) 71 on the outer peripheral surface thereof, like the processing liquid drum 54. The paper 24 fixed to the drawing drum 70 is conveyed with the recording surface facing outward, and ink is applied to the recording surface from the inkjet heads 72M, 72K, 72C, 72Y.

  The inkjet heads 72M, 72K, 72C, 72Y function as a droplet discharge head in the droplet discharge device. Each of the inkjet heads 72M, 72K, 72C, and 72Y is a line head having a length corresponding to the width of the paper 24. On the ink ejection surface, a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area is formed. Each inkjet head 72M, 72K, 72C, 72Y is installed so as to extend in a direction orthogonal to the conveyance direction of the paper 24 (the rotation direction of the drawing drum 70).

  The droplets of the corresponding color ink are ejected from the respective ink jet heads 72M, 72K, 72C, 72Y toward the recording surface of the paper 24 held tightly on the drawing drum 70, so that the processing liquid application unit 14 in advance. The ink comes into contact with the treatment liquid applied to the recording surface, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. Thereby, the color material flow on the paper 24 is prevented, and an image is formed on the recording surface of the paper 24.

  In this example, the configuration of CMYK standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special colors are used as necessary. Ink may be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the inkjet heads for each color is not particularly limited.

  The sheet 24 on which an image is formed by the drawing unit 16 is transferred from the drawing drum 70 to the drying drum 76 of the drying unit 18 via the intermediate conveyance unit 28.

<Dry section>
The drying unit 18 is a mechanism for drying moisture contained in the solvent separated by the color material aggregating action, and includes a drying drum 76 and a solvent drying device 78 as shown in FIG.

  Similar to the treatment liquid drum 54, the drying drum 76 includes a claw-shaped holding unit (gripper) 77 on the outer peripheral surface thereof, and the holding unit 77 can hold the leading end of the paper 24.

The solvent drying device 78 is disposed at a position facing the outer peripheral surface of the drying drum 76, and hot air jets disposed between a plurality of IR heaters (Infrared Radiation heaters) 82 and each IR heater 82. And a nozzle 80.

  Various drying conditions can be realized by appropriately adjusting the temperature and air volume of the hot air blown toward the paper 24 from each hot air jet nozzle 80 and the temperature of each IR heater 82. Drying is promoted by heating from the back side of the paper 24, and image destruction during fixing can be prevented.

  Holding on the outer peripheral surface of the drying drum 76 so that the recording surface of the paper 24 faces outward (that is, in a state in which the recording surface of the paper 24 is curved so as to be convex), and drying while rotating and transporting. Accordingly, the occurrence of wrinkles and floating of the paper 24 can be prevented, and drying unevenness caused by these can be surely prevented.

  The paper 24 that has been dried by the drying unit 18 is transferred from the drying drum 76 to the fixing drum 84 of the fixing unit 20 via the intermediate conveyance unit 30.

<Fixing part>
The fixing unit 20 includes a fixing drum 84, a halogen heater 86, a fixing roller 88, and an inline sensor 90. Like the processing liquid drum 54, the fixing drum 84 includes a claw-shaped holding unit (gripper) 85 on its outer peripheral surface, and the holding unit 85 can hold the leading end of the sheet 24.

  By the rotation of the fixing drum 84, the paper 24 is conveyed with the recording surface facing outward. The recording surface is preheated by the halogen heater 86, fixing processing by the fixing roller 88, and inspection by the inline sensor 90. Is done.

  The fixing roller 88 is a roller member for heating and pressurizing the dried ink to weld the self-dispersing thermoplastic resin fine particles in the ink to form a film of the ink, and is configured to heat and press the paper 24. Is done. Specifically, the fixing roller 88 is disposed so as to be in pressure contact with the fixing drum 84, and constitutes a nip roller with the fixing drum 84. As a result, the sheet 24 is sandwiched between the fixing roller 88 and the fixing drum 84, nipped at a predetermined nip pressure, and a fixing process is performed. The unevenness of the image surface is leveled by the fixing process, and glossiness is obtained.

  In the embodiment of FIG. 1, only one fixing roller 88 is provided. However, a configuration in which a plurality of fixing rollers 88 are provided may be employed depending on the thickness of the image layer and the Tg characteristics of the thermoplastic resin fine particles.

  In addition, in the case of using ultraviolet (UV) curable ink, instead of or in combination with the fixing roller 88 for heat fixing, ultraviolet (active light) such as a UV lamp or an ultraviolet LD (laser diode) array is used. Means for irradiating are provided. After sufficiently evaporating moisture in the drying unit 18, the UV curable monomer in the ink is cured and polymerized by irradiating the image with ultraviolet rays in the fixing unit equipped with ultraviolet irradiation means, thereby improving the image strength. Can do.

  On the other hand, the in-line sensor 90 is a measuring means for measuring a check pattern, moisture content, surface temperature, glossiness, etc. for an image (including a test chart) recorded on the paper 24, and a CCD line sensor or the like is applied. Is done.

<Discharge unit>
As shown in FIG. 1, a discharge unit 22 is provided following the fixing unit 20. The discharge unit 22 includes a discharge tray 92, and a transfer drum 94, a conveyance belt 96, and a tension roller 98 are provided between the discharge tray 92 and the fixing drum 84 of the fixing unit 20 so as to be in contact therewith. It has been. The sheet 24 is sent to the conveying belt 96 by the transfer drum 94 and discharged to the discharge tray 92.

<Other configuration>
Although not shown in FIG. 1, the inkjet recording apparatus 10 of this example includes an ink supply unit that supplies ink to the inkjet heads 72M, 72K, 72C, and 72Y, and the inkjet heads 72M and 72K, in addition to the above configuration. , 72C, 72Y, etc. are provided.

<Configuration of inkjet head>
Next, the configuration of the inkjet heads 72M, 72K, 72C, 72Y will be described. The ink jet heads 72M, 72K, 72C, 72Y of the present embodiment are constituted by line heads having a length corresponding to the paper width. Since each inkjet head 72M, 72K, 72C, 72Y has the same configuration, the configuration of the inkjet head 72 will be described here. In addition, the ink jet heads 72M, 72K, 72C, and 72Y will be described as the ink jet head 72 unless otherwise specified.

  FIG. 2 is a perspective view of the inkjet head 72 used in this embodiment. FIG. 2 shows a state in which the nozzle surface (droplet discharge surface) is looked up from below the head (obliquely downward direction). FIG. 3 is a partially enlarged view of the inkjet head 72 as viewed from the nozzle surface side. As shown in the figure, the inkjet head 72 is formed by connecting a plurality of head modules 72-i (i = 1, 2,..., N) along the longitudinal direction (paper width direction orthogonal to the conveyance direction of the paper 24). It is configured as an elongated full line type line head bar (page wide head of a single pass printing method). “I” represents a module number corresponding to the arrangement order of the head modules. “N” is an integer of 2 or more and represents the number of head modules. Here, an example in which 17 (n = 17) head modules 72-i are connected is shown. However, the number and arrangement of the head modules constituting the line head bar, and the structure of each head module are illustrated. It is not limited to the example. Reference numeral 73 in FIG. 2 denotes a base frame (housing for constituting a bar-shaped line head) serving as a frame for fixing a plurality of head modules 72-i, and reference numeral 75 denotes each head module 72-i. It is the flexible substrate connected to.

  Each head module 72-i is attached to and integrated with the base frame 73 to constitute one inkjet head 72. Each head module 72-i is supported by the head module support member 72 </ b> B from both sides of the inkjet head 72 in the short direction, and is detachably attached to the base frame 73. Each head module 72-i can be replaced individually. Each head module 72-i (i = 1, 2,..., N) can function as a droplet discharge head.

  As shown in FIG. 3, a plurality of nozzles are arranged in a matrix on the nozzle surface 72A of each head module 72-i (n-th head module 72-n). In FIG. 3, an oblique solid line denoted by reference numeral 151A represents a nozzle row in which a plurality of nozzles are arranged in a row.

  FIG. 4A is a plan perspective view of the head module. FIG. 4B is an enlarged view of a part thereof. In order to increase the dot pitch formed on the paper 24, it is necessary to increase the nozzle pitch in the inkjet head 72. In the head module 72-i of this example, as shown in FIGS. 4A and 4B, nozzles 151 (corresponding to “droplet discharge ports”) as ink discharge ports are arranged in a matrix (two-dimensionally). This structure has a high density of substantial nozzle intervals (projection nozzle pitch) projected so as to be aligned along the longitudinal direction of the inkjet head (direction perpendicular to the conveyance direction of the paper 24; main scanning direction). Has been achieved.

  In the example of FIGS. 4A and 4B, the plurality of nozzles 151 are arranged at a constant pitch d along the direction of the angle θ with respect to the main scanning direction, and are projected so as to be aligned in the main scanning direction (orthographic projection). The nozzle pitch P is d × cos θ, and in the main scanning direction, each nozzle 151 can be handled equivalently as a linear array with a constant pitch P.

  The nozzle arrangement structure is not limited to the illustrated example, and various nozzle arrangement structures such as an arrangement structure having one nozzle row in the sub-scanning direction can be applied.

  By connecting a plurality of such head modules 72-i in the paper width direction (main scanning direction) (see FIG. 1), a nozzle row that covers the entire drawing range for the paper width is formed, and one drawing scan is performed. Thus, a full-line head capable of recording an image with a predetermined recording resolution (for example, 1200 dpi) is configured.

  FIG. 5 is a longitudinal sectional view showing the internal structure of the head module. As shown in the figure, the pressure chamber 152 is formed as a rectangular parallelepiped space, and a nozzle channel 154 communicates with one corner of the bottom surface. The nozzle channel 154 extends vertically downward from the pressure chamber 152 and communicates with the nozzle 151.

  The ceiling wall surface of the pressure chamber 152 is composed of a diaphragm 155 and is formed to be able to bend and deform in the vertical direction. A piezoelectric element (piezo element) 156 is attached on the diaphragm 155, and the diaphragm 155 is deformed in the vertical direction by the piezoelectric element 156. The diaphragm 155 is deformed in the vertical direction, so that the volume of the pressure chamber 152 expands and contracts (expands / contracts), and ink is ejected from the nozzle 151.

  The piezoelectric element 156 is driven by applying a predetermined drive voltage between an individual electrode (not shown) provided on the piezoelectric element 156 and a diaphragm 155 acting as a common electrode, whereby the diaphragm 155 is driven. Deforms vertically.

  An individual supply channel 157 </ b> A for supplying ink to the pressure chamber 152 is communicated with one corner of the ceiling wall of the pressure chamber 152. The individual supply channel 157A communicates with the common supply channel 158A.

  The common supply flow path 158A is provided in units of rows of nozzles 151 arranged with a predetermined inclination with respect to the transport direction of the paper 24. Ink is supplied to the pressure chambers 152 of the nozzles 151 belonging to each row from the common supply channel 158A via the individual supply channel 157A.

  The common supply flow path 158A of each column communicates with an ink supply flow path (not shown), and the ink supply flow path communicates with an ink supply port (not shown). Ink from the ink tank is supplied to the ink supply port. The ink supplied to the ink supply port is supplied to the common supply channel 158A of each column via the ink supply channel, and further supplied to each pressure chamber 152 via the individual supply channel 157A.

  One end of an individual recovery channel 157B communicates with the nozzle channel 154. The individual recovery channel 157B communicates with the nozzle channel 154 at a position near the nozzle 151. The other end of the individual recovery channel 157B communicates with the common recovery channel 158B.

  Similar to the common supply channel 158A, the common recovery channel 158B is provided in units of rows of nozzles 151 arranged with a predetermined inclination with respect to the transport direction of the paper 24. The common recovery flow path 158B of each row communicates with an ink recovery flow path (not shown). The ink recovery channel communicates with an ink recovery port (not shown).

  A part of the ink flowing through each nozzle channel 154 flows to the individual recovery channel 157B and is recovered to the common recovery channel 158B. Then, the ink is recovered from each common recovery channel 158B to the ink tank via the ink recovery channel and the ink recovery port. That is, in the ink jet head of the present embodiment, ink is circulated and supplied to each head module 72-i.

<Ink supply unit>
Next, the configuration of the ink supply unit will be described. The ink supply unit includes an ink supply device (liquid supply device) having an ink supply function for supplying ink to the ink jet head 72 and an ink recovery function for recovering ink from the ink jet head 72. 10 functions as a liquid circulation supply means.

  FIG. 6 is a configuration diagram of a circulation supply type ink supply apparatus applied to the ink jet recording apparatus according to the present embodiment. The figure shows an ink supply system for one inkjet head (for one color). That is, the ink supply device 200 is provided for each color ink jet head, and ink is individually supplied for each ink jet head.

  As described above, the ink jet head 72 of the present embodiment is configured by connecting a plurality of head modules 72-i. Each head module 72-i is independent. For this reason, an ink circulation piping path for supplying ink equally (constant pressure, constant flow rate) to each head module 72-i is formed.

  As shown in FIG. 6, the head module 72-i is provided with an ink supply port 212A through which ink flows and an ink recovery port 212B through which ink is discharged.

  A tip of a supply side branch pipe 216 branched from the supply side manifold 214 is attached to the ink supply port 212A, and a tip of a recovery side branch pipe 220 branched from the recovery side manifold 218 is attached to the ink recovery port 212B. Yes. That is, the supply side manifold 214 and the recovery side manifold 218 are provided with as many branch pipes (supply side branch pipes 216 and recovery side branch pipes 220) as the number of head modules 72-i installed, and a plurality of head modules 72-i. Are connected in parallel between the supply side manifold 214 and the recovery side manifold 218 via corresponding branch pipes (216, 220).

  When drawing is performed by ejecting ink from the ink-jet head 72, the ink supplied to the supply-side manifold 214 is supplied to each head module 72-i at a predetermined pressure Pin and a predetermined flow rate. In addition, the ink supplied to the head module 72-i is recovered from the head module 72-i to the recovery side manifold 218 at a predetermined pressure Pout and a predetermined flow rate. .

  A pressure difference ΔP is generated in the head module 72-i by the pressure Pin of the supply side manifold 214 and the pressure Pout of the recovery side manifold 218. As a result, the ink supply port 212A and the ink recovery port 212B are generated in the head module 72-i. An ink flow is generated between the head module 72-i and the ink flow is always supplied to the head module 72-i. A back pressure Pnzl that depends on the pressure Pin 214 of the supply side manifold 214 and the pressure Pout of the recovery side manifold 218 is applied to the nozzle that is an ink ejection port (ejection port).

  Each supply side branch pipe 216 has a supply side valve 222 and a supply side sub-damper 224 interposed therebetween. Further, a recovery side valve 226 and a recovery side sub-damper 227 are interposed in the recovery side branch pipe 220, respectively. The supply side valve 222 and the recovery side valve 226 are opened and closed when the head module 72-i needs to be individually operated, and when starting circulation of ink to the head module 72-i or When it ends, it is opened and closed.

  The supply side branch pipe 216 corresponds to a “first flow path”, and the supply side valve 222 corresponds to a “supply side on-off valve”. The recovery side branch pipe 220 corresponds to a “second flow path”, and the recovery side valve 226 corresponds to a “recovery side on-off valve”.

  The supply-side sub-damper 224 has a role of relieving pressure fluctuations or the like when the ink supplied from the supply-side manifold 214 flows, and the recovery-side sub-damper 227 is used when the ink recovered to the recovery-side manifold 218 flows. It has a role to relieve pressure fluctuations.

  One end of the supply pipe 228 of the ink circulation piping system is attached to one end in the longitudinal direction (the right end in FIG. 6) of the supply side manifold 214. On the other hand, one end portion of the recovery pipe 230 of the ink circulation piping system is attached to one end portion in the longitudinal direction (right end portion in FIG. 6) of the recovery side manifold 218.

  In addition, a first bypass channel 232 and a second bypass channel 234 are provided between the other end portions (the left end portion in FIG. 6) of the supply side manifold 214 and the recovery side manifold 218. A first bypass valve 236 is interposed in the first bypass flow path 232. A second bypass valve 238 is interposed in the second bypass channel 234. The first bypass channel 232 and the second bypass channel 234 are used for adjusting the pressure and flow rate between the supply side manifold 214 and the recovery side manifold 218. The first bypass channel 232 has a smaller channel resistance than the second bypass channel 234. In this example, two bypass channels (232, 234) are provided, but it is sufficient that at least one bypass channel is provided.

  Further, a supply side pressure sensor 240 and a supply side temperature sensor 241 are attached to the other end of the supply side manifold 214, and a recovery side pressure sensor 242 and a recovery side temperature are attached to the other end of the recovery side manifold 218. A sensor 243 is attached. The pressure and temperature of the ink in the supply side manifold 214 are monitored by the supply side pressure sensor 240 and the supply side temperature sensor 241, and the pressure and temperature of the ink in the recovery side manifold 218 are monitored by the recovery side pressure sensor 242 and the recovery side temperature sensor 243. Is monitoring. For example, a thermistor can be used for the temperature sensors (241, 243). The supply side pressure sensor 240 functions as a supply side pressure detection unit, and the recovery side pressure sensor 242 functions as a recovery side pressure detection unit.

  The other end of the supply pipe 228 connected to the supply side manifold 214 is connected to a supply side pressure adjustment tank 244 that functions as a supply side main damper. The supply-side pressure adjustment tank 244 has a structure in which the sealed container is divided into an ink chamber 244B and a gas chamber 244C by an elastic film 244A. That is, the supply-side pressure adjustment tank 244 is divided into two chambers that are partitioned by an elastic film made of an elastic thin film member, one of which is an ink chamber 244B and the other is a gas chamber 244C (first gas). Equivalent to the room).

  One end of a supply-side main pipe 248 for drawing ink from the buffer tank 246 (and collecting it into the buffer tank 246) is connected to the ink chamber 244B. The opening at the other end of the supply side main pipe 248 is immersed in the ink stored in the buffer tank 246.

  In the supply side main pipe 248, a deaeration module 250, a one-way valve 252, a supply side filter 254, a supply side pump 256, and an ink temperature controller 258 are interposed in order from the buffer tank 246 to the supply side pressure adjustment tank 244. ing. The ink temperature controller 258 includes a heat exchanger and a chiller. Heating and cooling of the ink flowing in the ink flow path are adjusted by adjusting the temperature of water flowing through the heat exchanger connected to the chiller. Both temperature adjustments are possible. The ink temperature controller 258 corresponds to an “ink temperature adjusting unit”.

  The ink stored in the buffer tank 246 is supplied to the supply-side pressure adjustment tank 244 by the driving force of the supply-side pump 256, and air bubbles are removed from the ink along the way, dust is removed, and the ink temperature is controlled. ing.

  The inlet side of the supply side pump 256 is connected to one end of the branch pipe 253 separately from the supply side main pipe 248, and the other opening of the branch pipe 253 is ink stored in the buffer tank 246 via the one-way valve 255. Soaked in

  As the supply-side pump 256, a pump that can be driven and controlled in both a pressurizing direction for sending ink toward the supply-side manifold 214 and a decompression direction for drawing out ink from the supply-side manifold 214 is used. The structure of the pump is not particularly limited, but the supply-side pump 256 applied in the present embodiment is a tube pump using a stepping motor (the tube having elasticity is rotatively driven by the stepping motor and the ink in the tube is removed). Supply). The supply-side pump 256 is a multiple-type tube pump (multiple-tube) having a structure in which tubes having a small inner diameter (for example, an inner diameter of 3 mm or less) and a thick wall (for example, a tube thickness of 1 mm or more) are arranged in different phases. It is preferable to use a tube pump. By supplying or sucking the liquid by the supply side pump 256, the supply side flow path including the supply side manifold 214 is pressurized or depressurized.

  While monitoring the pressure in the supply side manifold 214 by the supply side pressure sensor 240, the drive direction and speed (rotation speed) of the supply side pump 256 are controlled. As described above, since it is required to accurately drive and control both the forward direction and the reverse direction, the above-described multiple-type tube pump is preferable.

  An open pipe 260 is attached to the gas chamber 244 </ b> C of the supply side pressure adjustment tank 244. An air connect valve 262, an air tank 264, and an air release valve 266 are interposed in the open pipe 260. The air connect valve 262 functions as a gas chamber division opening / closing mechanism, and the air tank 264 functions as a second gas chamber.

  The ink chamber 244B is connected to one end of the drain pipe 268. The opening at the other end of the drain pipe 268 is immersed in the ink stored in the buffer tank 246. A supply side drain valve 270 is interposed in the drain pipe 268.

  The supply-side pressure adjustment tank 244 has a function of adjusting and maintaining the pressure in the ink chamber 244B to a desired value by the action of the gas chamber 244C and the elastic film 244A.

  On the other hand, the other end of the recovery pipe 230 connected to the recovery side manifold 218 is connected to a recovery side pressure adjustment tank 272 that functions as a recovery side main damper. The structure of the recovery side pressure adjustment tank 272 is the same as the structure of the supply side pressure adjustment tank 244, and the sealed container is partitioned by an elastic film 272A, and is divided into an ink chamber 272B and a gas chamber 272C by the elastic film 272A. Have

  One end of a recovery side main pipe 274 for drawing ink from the buffer tank 246 (and drawing from the buffer tank 246) is connected to the ink chamber 272B.

  The other end of the recovery-side main pipe 274 is connected to the branch pipe 275 and is connected to the buffer tank 246 through the branch pipe 275. A one-way valve 276 is interposed in the recovery side main pipe 274, and the ink in the recovery side pressure adjustment tank 272 is recovered to the buffer tank 246 by the driving force of the recovery side pump 280.

  Similar to the supply-side pump 256, the recovery-side pump 280 is a pump that can be driven and controlled in both the pressurizing direction for sending ink toward the collecting-side manifold 218 and the depressurizing direction for drawing ink from the collecting-side manifold 218. It has been. The recovery side pump 280 of this example is configured by a multiple tube pump similar to the supply side pump 256. By supplying or sucking the liquid with the recovery side pump 280, the supply side flow path including the recovery side manifold 218 is pressurized or depressurized.

  An open pipe 282 is attached to the gas chamber 272 </ b> C (first gas chamber) of the recovery-side pressure adjustment tank 272. An air connect valve 284, an air tank 286, and an air release valve 288 are interposed in the open pipe 282. The air connect valve 284 functions as a gas chamber division opening / closing mechanism, and the air tank 286 functions as a second gas chamber.

  The ink chamber 272B is connected to one end of the recovery-side drain pipe 290. The other end of the recovery side drain pipe 290 is connected to the drain pipe 268 of the supply side pressure adjustment tank 244 via the recovery side drain valve 292.

  The collection-side pressure adjustment tank 272 has a function of adjusting and maintaining the pressure in the ink chamber 272B to a desired value by the action of the gas chamber 272C and the elastic film 272A.

  The pressure by the supply-side pump 256 and the recovery-side pump 280 during normal ink supply (circulation supply), such as when recording (printing) an image using the inkjet head 72, is the pressure Pin> of the supply-side manifold 214> Although it is the pressure Pout of the collection | recovery side manifold 218, each is made into negative pressure. That is, the supply pressure of the supply-side pump 256 is negative, but the recovery pressure of the recovery-side pump 280 is a lower negative pressure, so that the ink flows from the supply-side manifold 214 to the recovery-side manifold 218, and The back pressure Pnzl of the nozzle 151 of the head module 72-i is maintained at a negative pressure. Therefore, the ink is circulated to the nozzle 151 while the ink is held at the nozzle 151 of the head module 72-i.

  Note that the pressure range of the back pressure Pnzl that can hold the ink at the nozzle 151 differs depending on the specifications of the head module 72-i and the ink type. In the present embodiment, it is about −3000 Pa (G) (“(G)” means gauge pressure (atmospheric pressure reference pressure, relative pressure)).

  In the ink supply unit 202 of the present embodiment, a pressure purge pipe 294 is provided between the inlet side of the recovery side pump 280 and the outlet side of the degassing module 250 in the supply side main pipe 248 to connect the two. ing.

  A one-way valve 296 and a recovery-side filter 298 are interposed in order from the degassing module 250 to the recovery-side pump 280 in the pressure purge pipe 294. When air bubbles are eliminated by pressurizing the inside of the head module 72-i and discharging ink at once, in addition to driving the supply side pump 256, the driving direction of the recovery side pump 280 is reversed with respect to the normal time, and the buffer Ink is supplied from the tank 246 to the recovery side manifold 218. A drain tube 268 is used for discharging.

  The buffer tank 246 is connected to the main tank 300 via the refill pipe 302. The buffer tank 246 stores an amount of ink necessary for circulating the ink, and is configured to be replenished with ink from the main tank 300 according to ink consumption. The buffer tank 246 or a combination of the buffer tank 246 and the main tank 300 functions as a “tank” that stores ink to be supplied to the head module.

  One end of the replenishment pipe 302 is immersed in the ink stored in the main tank 300, and the other end is connected to the recovery-side main pipe 274. A filter 304 is attached to one end opening of the replenishment pipe 302 immersed in the ink in the main tank 300. A refill pump 306 is interposed in the refill pipe 302. By driving the refill pump 306, the buffer tank 246 is refilled with ink.

  An overflow pipe 308 is provided between the buffer tank 246 and the main tank 300 so that ink is returned to the main tank 300 when it is excessively replenished.

  The overflow pipe 308 is connected to one end of the recovery side relief pipe 312. The other end of the collection side relief pipe 312 is connected to a collection side main pipe 274 between the collection side pump 280 and the collection side pressure adjustment tank 272.

  A recovery side relief valve 316 is interposed in the recovery side relief pipe 312. The recovery side relief valve 316 opens when the pressure of the ink flowing in the pipeline exceeds a preset pressure, and prevents high pressure from being applied to the inkjet head and the pipeline.

  A liquid level sensor 318 is provided in the buffer tank 246, and information on the amount of ink in the buffer tank 246 can be obtained by the liquid level sensor 318. Similarly, a liquid level sensor 320 is also provided in the main tank 300, and information on the amount of ink in the main tank 300 can be obtained by the liquid level sensor 320.

<Ink supply unit control system>
FIG. 7 is a block diagram showing a schematic configuration of a control system of the ink supply apparatus 200 shown in this example. The ink supply apparatus 200 includes an ink supply control unit 350 that performs overall control of the control system, an ink temperature controller 258 that controls heating / cooling temperature by the ink supply control unit 350, and a control that is sent from the ink supply control unit 350. Controls the opening and closing of the supply side pump control unit 352 that controls the supply side pump 256 based on the signal and the supply side valves (supply side valve 222, drain valve 270, air connect valve 262, atmosphere release valve 266, etc.). A supply-side valve control unit 354 that controls the collection-side pump 280 based on a control signal sent from the ink supply control unit 350, and a collection-side valve (collection-side valve 226, drain) Valve 292, air connect valve 284, air release valve 288, etc.) As a means for presenting various information such as a control unit 364, a bypass valve control unit 366 that controls the first bypass valve 236 and the second bypass valve 238, and notifying that when an abnormality occurs in each part of the apparatus The display device 375 is provided.

  The ink supply apparatus 200 includes a parameter storage unit 380, a program storage unit 382, a supply side pressure sensor 240, a supply side temperature sensor 241, a recovery side pressure sensor 242, and a recovery side temperature sensor 243. doing.

  The parameter storage unit 380 stores various parameters used for control of the ink supply apparatus 200 and a data table referred to at the time of control.

  The program storage unit 382 stores a program used for controlling the ink supply device 200. The ink supply control unit 350 reads out and executes various control programs stored in the program storage unit 382, and controls the ink supply apparatus 200 with reference to various parameters and data tables stored in the parameter storage unit 380. And control. The temperature control of the initial filling process to be described later is executed according to a program.

  The ink supply control unit 350 adjusts the insides of the supply side flow path and the recovery side flow path to predetermined pressures (set pressures) based on the detection results of the supply side pressure sensor 240 and the recovery side pressure sensor 242, respectively. The driving of the supply side pump 256 and the recovery side pump 280 is controlled. Further, the ink supply control unit 350 controls the operation of the ink temperature controller 258 so that the target temperature set value is obtained based on the detection results of the supply side temperature sensor 241 and the recovery side temperature sensor 243.

  When supplying ink to the inkjet head 72 during printing, a predetermined pressure difference is set so that the internal pressure of the supply side manifold 214 is relatively higher than the internal pressure of the recovery side manifold 218, and The ink supply control unit 350 supplies the supply side pump 256 and the recovery side so that a predetermined back pressure (negative pressure) is applied to the ink inside the nozzles of the head modules 72-1, 12-2,. The drive of the pump 280 is controlled.

  Although FIG. 7 shows a configuration in which the valve control unit and the pump control unit are individually provided on the supply side and the collection side, the control unit may be shared between the supply side and the collection side.

[Ink filling process associated with module replacement]
Next, an ink initial filling method associated with the replacement operation of the head module in the ink jet recording apparatus having the above configuration will be described.

  In the present embodiment, a circulation type ink jet head capable of supplying and collecting ink is filled with ink sufficiently heated to a target set temperature. For this purpose, the following measures are mainly adopted.

  (1) A bypass channel is provided between the supply side manifold 214 and the recovery side manifold 218 in parallel with the head module, and the ink is circulated using the bypass channel and heated by the ink temperature controller before the initial filling. As a result, the ink in the flow path is sufficiently heated.

  (2) From the temperature sensor (241, 243) in a common flow path (supply side manifold 214, recovery side manifold 218) in which a plurality of head modules constituting a line type ink jet head are connected in parallel. Get ink temperature information.

  (3) When replacing the head module, the ink temperature is changed from the ink temperature for printing to the ink temperature for replacement (ink filling), and then ink filling is performed.

  The replacement of the head module here is as follows. That is, after completing the ink filling of all the head modules constituting the line head bar, if some of the head modules deteriorate due to a certain period of use or sudden failure, they are replaced newly.

  (4) The ink temperature at the time of ink filling is higher than the ink temperature at the time of printing. For example, the ink temperature at the time of printing is adjusted to 30 ° C. ± 1.5 ° C., and at the time of ink filling, the temperature is adjusted to be higher (above 31.5 ° C.) and lower than the upper limit temperature. The upper limit temperature of the ink temperature at the time of ink filling is the upper limit of the temperature at which the ink does not change, and for example, about 70 ° C. is assumed. Since the upper limit temperature depends on the composition of the ink, it is defined in advance based on experiments and the like.

  The above (1) to (4) will be described in more detail.

<About (1)>
In the conventional configuration shown in Patent Documents 1 to 3, since there is no bypass flow path, when the heat capacity of the ink is large, or when the heating capability of the heating means (heating unit) is insufficient, a predetermined target is set. The ink is filled without being heated to the above temperature.

  On the other hand, according to this embodiment, for example, at the time of initial filling, initially, an unfilled head module is not filled with ink (at least the supply side valve connected to the head module to be initially filled and the recovery side With the valve closed, the bypass channel (in this example, the first bypass channel 232 is used) is filled first, and ink circulation is performed using the bypass channel. By heating to the set temperature with the ink temperature controller 258 and performing circulation using the first bypass flow path 232, the ink can be sufficiently heated. Further, the ink temperature can be heated to the target value without being greatly affected by the ability of the ink temperature controller 258.

  In this way, after the ink is sufficiently heated by circulation through the bypass flow path, the supply side valve and the recovery side valve are opened to fill the head module with ink. By doing so, it is possible to fill the head module with ink at a high ink temperature (a good wettability state).

  When replacing some of the head modules that make up the inkjet head, when changing the ink temperature, not only the bypass flow path, but also the entire head module that is not subject to replacement is used to circulate and heat the ink. May be.

<About (2)>
In this embodiment, the ink temperature information is stored in the temperature sensor (241, 243) in a common flow path (at least one manifold of the supply side manifold 214 and the recovery side manifold 218) to which a plurality of head modules are connected. Is installed and acquired.

  Based on the ink temperature information detected by the temperature sensors (241, 243), the operation of the ink temperature controller 258 (ON / OFF, heating amount, etc.) is controlled. For example, when the value of the temperature sensor (241, 243) reaches the set value and it is confirmed that the ink is sufficiently heated, the drive of the ink temperature controller 258 is stopped. Alternatively, the control of the ink temperature controller 258 may be configured to perform feedback control using the value of the temperature sensor (241, 243).

  In the example of FIG. 6, the temperature sensor (241, 243) is installed in each of the supply side manifold 214 and the recovery side manifold 218, but a configuration in which the temperature sensor is installed only in one of the manifolds is also possible. It is. A temperature sensor may be installed in at least one of the supply side manifold 214 and the recovery side manifold 218.

  By adopting such a configuration, the ink temperature at a position close to the head module can be grasped, and the ink temperature can be adjusted with higher accuracy.

<About (3)>
When replacing the head module, the ink temperature setting value is changed from the printing temperature to the ink filling temperature. Here, the ink filling temperature is set higher than the printing temperature (printing temperature <ink filling temperature).

    For example, after reaching the target value temperature for ink filling, both the supply side (IN side) and recovery side (OUT side) valves (222 and 224) of the corresponding module are closed, and the module is replaced. After that, the valves (222, 224) are opened again to perform ink filling (see FIG. 8). The operation sequence shown here is merely an example, and there are several degrees of freedom for specific operation procedure modes.

<About (4)>
As described above, in this embodiment, the temperature setting during ink filling and the temperature setting during printing are set to different values. The purpose of this is to increase the temperature when taking ink into consideration, but in the case of printing, the meniscus state at the time of nozzle ejection is also taken into consideration. It is necessary to do. For example, when focusing on the nozzle, the meniscus recovery time (refill time) after ejecting a single droplet depends on the surface tension of the meniscus, and if the ink temperature is too high and the surface tension is too low, The refill time becomes long, and there is a possibility that printing at a predetermined frequency cannot be performed.

  Therefore, at the time of printing, the ink temperature is adjusted to a lower temperature (for example, 30 ° C. ± 1.5 ° C.) than that at the time of ink filling so as to obtain a surface tension that provides a meniscus recovery time (refill time) that can achieve the required ejection frequency. Is done.

<Example 1 of Operation Procedure of Ink Filling Process Associated with Module Replacement>
FIG. 8 is a flowchart showing a first example of the operation procedure of the ink filling process accompanying the replacement of the head module. The operation procedure when the head module is replaced and ink is initially filled in the new module after the replacement is shown. In the example of FIG. 8, before the head module replacement operation is performed, first, the ink temperature setting value is changed from printing temperature to ink charging temperature (step S12). When the printing temperature is set to 30 ° C. ± 1.5 ° C., the ink filling temperature is set to a temperature higher than this and lower than the upper limit temperature (for example, about 60 ° C.). In accordance with this set value, the ink temperature controller 258 is heated.

  Next, the first bypass valve 236 of the first bypass channel 232 is opened, and ink is circulated in a state where the bypass path between the supply side manifold 214 and the recovery side manifold 218 is opened (step S14). At this time, both the supply side valve 222 and the recovery side valve 226 of each head module are opened, and ink circulation is performed using the flow path in the head module. Thus, by heating the ink by the ink temperature controller 258 and circulating the ink, the temperature can be reliably raised to the set temperature (target value). While the ink temperature is monitored by the temperature sensors (241, 243), heating by the ink temperature controller 258 and ink circulation are continued.

  Then, after reaching the target ink temperature by the circulation heating, the supply side valve 222 and the recovery side valve 226 of the head module to be replaced are closed, the target head module is removed, and the head module is replaced with a new head module. (Step S16).

  For example, when the ink temperature reaches the target value by the above-mentioned circulation heating, the operator is notified through a user interface such as the display device 375 (see FIG. 7), and the head module is detached. The operator removes the old head module and replaces it with a new head module (“head connection process”). During the head module removal / replacement (replacement) operation, the ink circulation may be continued or stopped. The ink temperature is generally kept constant during the head module replacement operation.

  After the replacement of the head module, the valves (222, 226) are opened, and the new head module is initially filled with ink (step S18). For example, when the operator (operator) instructs the end of the work through the user interface after the replacement work of the head module, the supply side valve 222 and the recovery side valve 226 are opened based on the initial filling control program, The ink adjusted to the ink filling temperature is filled in the new head module.

  When ink adjusted to a predetermined temperature is allowed to flow into a new head module, the entire ink circulation is stopped and only the corresponding head module can open the valves (222, 226) to fill the ink. .

  According to this embodiment, the ink heated to the ink filling temperature has improved wettability with respect to the flow path in the head, and it is possible to efficiently fill by preventing the remaining of bubbles.

<Example 2 of Operation Procedure of Ink Filling Process Associated with Module Replacement>
FIG. 9 is a flowchart showing a second example of the operation procedure of the ink filling process accompanying the replacement of the head module. In the example of FIG. 9, the ink temperature is changed and the filling process is performed after the head module replacement operation.

  That is, first, the supply side valve and the recovery side valve of the head module to be replaced are closed, the target head module is removed, and a replacement operation with a new head module is performed (step S22).

  When the operator (operator) gives an instruction to end the work through the user interface after the replacement of the head module, the operations of steps S24 to S28 are performed based on the initial filling control program.

  In step S24, a process of changing the ink temperature setting value from the printing temperature to the ink charging temperature is performed. As already described, the ink filling temperature is set higher than the printing temperature. The ink temperature controller 258 is driven and controlled using the set value as a target value for temperature adjustment.

  Next, the first bypass valve 236 of the first bypass channel 232 is opened, and the ink is circulated in a state where the bypass path between the supply side manifold 214 and the recovery side manifold 218 is opened (step S26). At this time, the supply side valve 222 and the recovery side valve 226 connected to the head module that is not to be replaced may be closed or opened. Here, the ink circulation is performed with the supply side valve 222 and the recovery side valve 226 of the head module not to be replaced open. By heating the ink with the ink temperature controller 258 and circulating the ink, the temperature can be reliably increased to the set temperature (target value). While the ink temperature is monitored by the temperature sensors (241, 243), heating by the ink temperature controller 258 and ink circulation are continued.

  In this way, the ink temperature in the flow path is monitored while circulating heating is performed, and after reaching the target ink temperature, the supply side valve and the recovery side valve of the corresponding head module are opened to perform ink filling (step S28). .

  According to the operation procedure shown in FIG. 9, the ink heated to the ink filling temperature has improved wettability with respect to the flow path in the head, and it is possible to perform efficient filling by preventing remaining bubbles.

  In addition to the operation procedures illustrated in FIGS. 8 and 9, various changes can be made regarding the adoption of specific operation procedures. When the ink is initially filled in the unfilled head module, if the ink is sufficiently heated to the target filling temperature by performing circulation heating using the bypass flow path, then the ink can flow into the module. Good.

  The timing of opening each of the supply side valve 222 and the recovery side valve 226 when introducing the ink heated to the filling temperature into the head module, the driving directions of the supply side pump 256 and the recovery side pump 280, and the pump speed The (rotation speed) is also appropriately controlled according to the initial filling control program.

<Regarding ink temperature control after ink filling>
After the initial filling illustrated in FIGS. 8 and 9, the printing is started after the process of returning the ink temperature to the printing temperature. FIG. 10 is a flowchart illustrating the operation procedure of the temperature adjustment process after ink filling.

  After the ink filling into the head module is completed, the process of FIG. 10 is executed. That is, a process of changing the ink temperature setting value from the ink filling temperature to the printing temperature is performed (step S32). The printing temperature is set to a temperature lower than the ink filling temperature. For example, the ink filling temperature is set to 60 ° C., and the printing temperature is set to 30 ° C. ± 1.5 ° C. The printing temperature can be set as a predetermined temperature range including an allowable temperature range (allowable temperature range). Using the set value (predetermined temperature range) as a target value, the ink temperature controller 258 is driven (cooling drive here) so as to lower the ink temperature.

  The ink in the flow path is cooled to the printing temperature by performing ink circulation while operating the ink temperature controller 258 (step S34). While the ink temperature is monitored by the temperature sensors (241, 243), heating by the ink temperature controller 258 and ink circulation are continued. Thereby, the ink temperature can be reliably lowered to the set temperature (target value). During this ink circulation (circulation cooling), not only the replaced head module, but also the supply side valves and recovery side valves of all head modules connected to the same manifold are opened, It is desirable to perform ink circulation using a flow path. Further, the second bypass valve 238 of the second bypass channel 234 used for ink circulation during printing is also opened, and ink for temperature adjustment is performed in the second bypass channel 234 and the entire head module. It is desirable.

  Thus, after the ink temperature is adjusted to the target printing temperature, printing is started.

<Control system of inkjet recording apparatus>
Next, the overall configuration of the control system of the ink jet recording apparatus including the ink supply apparatus described above will be described. FIG. 11 is a block diagram showing a schematic configuration of a control system of the ink jet recording apparatus. The inkjet recording apparatus 10 includes a communication interface 440, a system control unit 442, a conveyance control unit 444, an image processing unit 446, and an inkjet head drive unit 448, and an image memory 450 and a ROM (Read Only Memory) 452.

  The communication interface 440 is an interface unit that receives image data sent from the host computer 454. The communication interface 440 may be a serial interface such as USB (Universal Serial Bus) or a parallel interface such as Centronics. The communication interface 440 may be equipped with a buffer memory (not shown) in order to speed up communication.

  The system control unit 442 includes a central processing unit (CPU (Central Processing Unit)) and its peripheral circuits. The system control unit 442 functions as a control unit that controls the entire inkjet recording apparatus 10 according to a predetermined program and performs various calculations. It functions as a computing device to perform. Also, it functions as a memory controller for the image memory 450 and the ROM 452. That is, the system control unit 442 controls each unit such as the communication interface 440 and the transport control unit 444, performs communication control with the host computer 454, read / write control of the image memory 450 and the ROM 452, and the like. A control signal to be controlled is generated.

  The image data sent from the host computer 454 is taken into the inkjet recording apparatus 10 via the communication interface 440 and subjected to predetermined image processing by the image processing unit 446.

  The image processing unit 446 has a signal (image) processing function for performing various processes and corrections for generating a print control signal from the image data, and supplies the generated print data to the inkjet head driving unit 448. To do. Necessary signal processing is performed in the image processing unit 446, and the ejection droplet amount (droplet ejection amount) of the inkjet head 72 and ejection timing are controlled via the inkjet head driving unit 448 based on the image data. . Thereby, a desired dot size and dot arrangement are realized.

  The inkjet head drive unit 448 may include a feedback control system for keeping the drive conditions of the inkjet head 72 constant.

  The inkjet head drive unit 448 includes a drive waveform generation unit that generates a drive waveform, an amplification unit that amplifies the drive waveform to generate a drive voltage, and a drive voltage that supplies a drive voltage having a predetermined drive waveform to the inkjet head And a supply unit. A drive waveform is generated based on image data (digital data) sent from the system control unit (or a corresponding drive waveform is selected from the drive waveforms stored in advance), and the drive voltage having the drive waveform is Generated.

  The conveyance control unit 444 controls the conveyance timing and conveyance speed of the paper 24 based on the print control signal generated by the image processing unit 446. The transport driving unit 456 includes a motor that rotates a transport drum of each unit, a motor that rotates an intermediate transport body, and the like, and the transport control unit 444 functions as a driver of the motor.

  The image memory 450 functions as a primary storage unit that temporarily stores image data input via the communication interface 440, a development area for various programs stored in the ROM 452, and a calculation work area for the CPU (for example, image processing). Function as a work area of the unit 446. As the image memory 450, a volatile memory (RAM) capable of sequential reading and writing is used.

  The ROM 452 stores programs executed by the CPU of the system control unit 442, various data necessary for control of each unit of the apparatus, control parameters, and the like, and data is read and written through the system control unit 442. The ROM 452 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used. Alternatively, a removable storage medium that includes an external interface may be used.

  Further, the inkjet recording apparatus 10 includes a processing liquid application control unit 460, a drying processing control unit 462, a fixing processing control unit 464, a maintenance control unit 486, an ink supply control unit 350, and the like. In accordance with the instructions, the operations of the processing liquid application unit 14, the drying unit 18, the fixing unit 20, the maintenance processing unit 170, and the ink supply unit 202 are controlled.

  Based on the print data obtained from the image processing unit 446, the processing liquid application control unit 460 controls the processing liquid application timing by the processing liquid application unit 14 and also controls the amount of processing liquid applied.

  The drying processing control unit 462 controls the solvent drying device 78 included in the drying unit 18 and controls the processing temperature, the air flow rate, and the like.

  The fixing process control unit 464 controls the temperature of the halogen heater 86 included in the fixing unit 20 and also controls the pressing of the fixing roller 88.

  The ink jet recording apparatus 10 shown in this example includes a user interface 470. The user interface 470 includes an input device 472 for an operator (user) to make various inputs and a display unit (display) 474. The input device 472 may employ various forms such as a keyboard, a mouse, a touch panel, and buttons. By operating the input device 472, the operator can perform input of printing conditions, selection of image quality mode, input / editing of attached information, search of information, etc. Various information such as input contents and search results can be obtained. This can be confirmed through display on the display unit 474. The display unit 474 also functions as a means for displaying a warning such as an error message.

  The parameter storage unit 480 stores various control parameters necessary for the operation of the inkjet recording apparatus 10. The system control unit 442 appropriately reads out parameters necessary for control and updates (rewrites) various parameters as necessary.

  The program storage unit 482 is a storage unit that stores a control program for operating the inkjet recording apparatus 10. The system control unit 442 (or each unit of the device) reads a necessary control program from the program storage unit 482 when executing control of each unit of the device, and appropriately executes the control program.

  The parameter storage unit 480 and the program storage unit 482 can also be used as the parameter storage unit 380 and the program storage unit 382 described with reference to FIG.

  A maintenance control unit 486 in FIG. 11 is a control block that controls the operation of the maintenance processing unit 170 based on a command signal sent from the system control unit 442. When the control of the ink jet recording apparatus 10 shifts to the maintenance mode, the ink jet head 72 is moved from the printing position directly above the drawing drum 70 to the maintenance position, and each part of the maintenance processing unit 170 corresponding to the movement of the ink jet head 72. To work.

  The ink supply control unit 350 controls the operation of the ink supply unit 202 based on the command signal sent from the system control unit 442. As described above, the ink jet recording apparatus 10 of the present embodiment circulates and supplies ink to the ink jet head 72. The ink supply control unit 350 operates each unit of the ink supply unit 202 when initially filling the unfilled head module with ink. In addition, the ink supply control unit 350 operates each unit of the ink supply unit 202 so that ink is circulated and supplied to the inkjet head 72 during image recording (printing) after ink filling.

  A combination of the ink supply control unit 350 and the ink supply unit 202 corresponds to the ink supply apparatus 200 described with reference to FIG. The function of the ink supply control unit 350 can be integrated into the system control unit 442. The ink supply control unit 350, the system control unit 442, or a combination thereof corresponds to the “control unit”.

<Advantages of this embodiment>
[1] Since the ink is circulated and heated using the bypass flow path, the temperature can be reliably increased to the target temperature regardless of the ability of the ink temperature controller 258.

  [2] By providing a temperature sensor in the manifold and detecting the temperature before and after the head, more accurate temperature control becomes possible. Although it is possible to provide a temperature sensor in each head module, the configuration in which the temperature sensor is arranged in a manifold, which is a common flow path, can reduce the number of sensors and reduce the cost of the apparatus. It is preferable from the viewpoint of reduction.

  [3] Since the ink temperature at the time of printing and the ink temperature at the time of initial filling (at the time of module replacement) are different (printing temperature <temperature for ink filling), it is possible to guarantee an appropriate operation according to each. it can.

<Modification 1 of Embodiment>
A plurality of head modules constituting the line head bar can be replaced at a time. When a plurality of head modules are replaced, the ink filling process after replacement can be performed one by one. It is also possible to perform a plurality of processes simultaneously. Even when ink is filled one by one for the plurality of replaced head modules, the ink circulation heating process can be performed collectively. That is, after the circulation heating is performed, ink can be charged into the head modules one by one in order.

<Modification 2>
In the above example, the temperature sensors (241, 243) that detect the temperatures inside the supply side manifold 214 and the recovery side manifold 218 are used, but instead of this or in combination with this, each head module has A configuration in which a temperature sensor is installed is also possible.

<Modification 3>
The form of the long inkjet head composed of a plurality of head modules is not limited to the form illustrated in FIGS. For example, the present invention can be applied to an inkjet head having a structure in which a plurality of head modules are arranged in a staggered manner.

<Modification 4>
In the above-described embodiment, an ink jet recording apparatus that forms an image by directly ejecting ink droplets onto a sheet (direct recording method) has been described. However, the scope of application of the present invention is not limited to this, and the intermediate transfer is temporarily performed. The present invention can also be applied to an intermediate transfer type ink jet recording apparatus that forms an image (primary image) on a body and transfers the image onto a recording sheet in a transfer unit to form a final image. it can.

  In the embodiment of the present invention described above, the configuration requirements can be appropriately changed, added, and deleted without departing from the spirit of the present invention. The present invention is not limited to the embodiments described above, and many modifications are possible by those having ordinary knowledge in the field within the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 24 ... Paper, 72 (72M, 72K, 72C, 72Y) ... Inkjet head, 72-i ... Head module, 151 ... Nozzle, 200 ... Ink supply device, 202 ... Ink supply unit, 212A ... Ink Supply port, 212B ... Ink recovery port, 214 ... Supply side manifold, 216 ... Supply side branch pipe, 218 ... Recovery side manifold, 220 ... Recovery side branch pipe, 222 ... Supply side valve, 226 ... Recovery side valve, 228 ... Supply 230, recovery pipe, 232 ... first bypass flow path, 234 ... second bypass flow path, 236 ... first bypass valve, 238 ... second bypass valve, 240 ... supply side pressure sensor, 241 ... supply side temperature sensor 242 ... Collection side pressure sensor, 243 ... Collection side temperature sensor, 258 ... Ink temperature controller, 300 ... Main Link, 350 ... ink supply control unit, 352 ... supply-side pump control unit, 354 ... supply-side valve control unit, 362 ... recovery side pump control unit, 366 ... bypass valve control unit, 440 ... communication interface, 442 ... system control unit

Claims (11)

An inkjet head composed of a plurality of head modules;
A plurality of head modules connected in parallel, and a supply side manifold for supplying ink to each head module;
A plurality of head modules connected in parallel, and a recovery side manifold for recovering ink from each head module;
A supply-side on-off valve provided corresponding to each of the head modules and capable of opening and closing a first flow path connecting each head module and the supply-side manifold;
A recovery-side on-off valve provided corresponding to each of the head modules, and capable of opening and closing a second flow path connecting each head module and the recovery-side manifold;
A bypass passage connected in parallel with the plurality of head modules between the supply side manifold and the recovery side manifold, and connecting the supply side manifold and the recovery side manifold;
A bypass on-off valve capable of opening and closing the bypass flow path;
A supply-side pump that varies the pressure of the supply-side flow path section including the supply-side manifold;
A recovery-side pump that varies the pressure of the recovery-side flow path section including the recovery-side manifold;
An ink temperature adjusting unit for adjusting the temperature of the ink supplied to the head module;
A control unit that controls operations of the supply side on-off valve, the recovery side on-off valve, the bypass on-off valve, the supply side pump, the recovery side pump, and the ink temperature adjustment unit,
The controller circulates ink using the bypass flow path and heats the ink by the ink temperature controller before circulating the ink to the target temperature before initially filling the head module with ink. An ink jet recording apparatus that performs control for filling the heated head module into the head module to be filled later. A temperature sensor is provided on at least one of the supply side manifold and the recovery side manifold,
The ink jet recording apparatus according to claim 1, wherein the control unit controls the ink temperature adjusting unit based on information obtained from the temperature sensor.   The ink jet recording apparatus according to claim 2, wherein the control unit sets a temperature that is a target value for temperature control, and feedback-controls the ink temperature adjusting unit using information obtained from the temperature sensor.   4. The ink jet recording apparatus according to claim 1, wherein the ink temperature adjustment unit has a temperature adjustment function for both heating and cooling of the ink. 5.   The inkjet ink according to any one of claims 1 to 4, wherein an ink filling temperature at the time of performing the initial filling is set to a temperature higher than a printing temperature at the time of performing image recording using the inkjet head. Recording device.   The ink jet recording apparatus according to claim 5, wherein the ink filling temperature is 70 ° C. or less.   When replacing the entire inkjet head after completion of ink filling or a part of the plurality of head modules, the control unit sets the ink temperature from the printing temperature. The ink jet recording apparatus according to claim 5, wherein the ink recording temperature is changed to the ink filling temperature.   The ink jet recording apparatus according to claim 7, wherein after the initial ink filling of the head module newly mounted by the replacement is completed, the control unit performs control to change the ink temperature to the printing temperature. .   The ink jet recording apparatus according to claim 1, wherein the ink jet head is a line head bar in which the head module can be replaced in units of the head module. The controller performs the circulating heating in a state in which at least the supply-side on-off valve and the collection-side on-off valve connected to the head module to be initially filled are closed,
10. The control according to claim 1, wherein after the ink is heated to the target temperature, control is performed to open a supply-side on-off valve and a recovery-side on-off valve connected to the head module to be initially filled. Inkjet recording apparatus. An inkjet head composed of a plurality of head modules;
A plurality of head modules connected in parallel, and a supply side manifold for supplying ink to each head module;
A plurality of head modules connected in parallel, and a recovery side manifold for recovering ink from each head module;
A supply-side on-off valve provided corresponding to each of the head modules and capable of opening and closing a first flow path connecting each head module and the supply-side manifold;
A recovery-side on-off valve provided corresponding to each of the head modules, and capable of opening and closing a second flow path connecting each head module and the recovery-side manifold;
A bypass passage connected in parallel with the plurality of head modules between the supply side manifold and the recovery side manifold, and connecting the supply side manifold and the recovery side manifold;
A bypass on-off valve capable of opening and closing the bypass flow path;
A supply-side pump that varies the pressure of the supply-side flow path section including the supply-side manifold;
A recovery-side pump that varies the pressure of the recovery-side flow path section including the recovery-side manifold;
An ink temperature adjusting unit that adjusts the temperature of ink supplied to the head module, and an initial ink filling method for the head module in an ink jet recording apparatus, and before the ink is initially filled in the head module, A circulation heating step of circulating the ink to the target temperature by circulating the ink using the bypass flow path and heating the ink by the ink temperature adjusting unit;
A filling step of filling the ink by flowing the ink heated by the circulation heating step into the head module to be filled; and
An ink filling method comprising:

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